Method of constructing a prefabricated wall module

ABSTRACT

A prefabricated sheet metal wall module comprises: an upper horizontal cap member of inverted U-shaped cross-sectional configuration with a pair of parallel longitudinal dependent side flanges; a lower horizontal floor track member of U-shaped crosssectional configuration with a pair of parallel upwardly extending longitudinal side flanges; and a series of parallel upright studs each having a pair of opposite longitudinal side flanges. The upper and lower ends of each stud telescope into the upper and lower horizontal members respectively with the side flanges of the stud in intimate surface contact with the side flanges of the horizontal members thereby providing four rectangular areas of two layers of metal. With a stud in assembled position under compression between the associated horizontal members, a power-actuated hand tool having a pair of jaws equipped with a hollow die and cooperating punch, respectively, is applied at each juncture of a horizontal member with a stud of metal at each juncture to punch interlocking hyperboloidal crimps in the two overlapping layers resulting in prestressed joints that make the wall module rigid enough to carry to a construction site where wall modules are assembled to form a low-cost building.

'United States Patent 1 Duke [ Dec. 16, 1975 METHOD OF CONSTRUCTING APREFABRICATED WALL MODULE Jack Doke, Diamond Bar, Calif.

[22] Filed: July 8, 1974 [21] Appl. No.1 486,629

Related US. Application Data [63] Continuation of Ser. No. 364,295, May29, 1973,

[75] Inventor:

abandoned.

[52] US. Cl. 29/509; 29/21.1; 29/521; 52/241; 52/666; 52/758 D; 83/620;113/116 FF [51] Int. Cl. B21D 39/00; B23? 11/00 [58] Field of Search29/155 R, 509, 21.1, 432,

29/521; 113/116 FF; 83/620; 52/241, 481, 666, 735, 758 D, 758 A, 758 H[56] References Cited UNITED STATES PATENTS 2,865,451 12/1958 lhrig29/509 UX 2,996,161 8/1961 Etling 52/758 H X FORElGN PATENTS ORAPPLICATTONS United Kingdom ll3/l16 FF Primary Examiner-Charlie T. MoonAttorney, Agent, or Firm-Reed C. Lawlor [5 7 ABSTRACT A prefabricatedsheet metal wall module comprises: anupper horizontal cap member ofinverted U-shaped cross-sectional configuration with a pair of parallellongitudinal dependent side flanges; a lower horizontal floor trackmember of U-shaped cross-sectional configuration with a pair of parallelupwardly extending longitudinal side flanges; and a series of parallelupright studs each having a pair of opposite longitudinal side flanges.The upper and lower ends of each stud telescope into the upper and lowerhorizontal members respectively with the side flanges of the stud inintimate surface contact with the side flanges of the horizontal membersthereby providing four rectangular areas of two layers of metal. With astud in assembled position under compression between the associatedhorizontal members, a power-actuated hand tool having a pair of jawsequipped with a hollow die and cooperating punch, respectively, isapplied at each juncture of a horizontal member with a stud of metal ateach juncture to punch interlocking hyperboloidal crimps in the twooverlapping layers resulting in prestressed joints that make the wallmodule rigid enough to carry to a construction site where wall modulesare assembled to form a low-cost building.

4 Claims, 13 Drawing Figures U.S. Patent Dec. 16, 1975 Sheet 1 of3 US.Patent Dec. 16, 1975 Sheet 2 of3 3,925,875

METHOD OF CONSTRUCTING A PREFABRICATED WALL MODULE CROSS REFERENCES TORELATED APPLICATIONS This application is a continuation of copendingapplication Ser. No. 364,295, filed May 29, 1973, now abandoned.

Patent Application Ser. No. 35,648, filed may 8,

Patent Application Ser. No. 467,247, filed Nov.

1973, now abandoned.

Patent Application Ser. No. 412,043, filed Nov.

1973, now abandoned.

Patent Application Ser. No. 412,041, filed Nov.

Patent Application Ser. No. 412,044, filed Nov.

1973, now abandoned.

Patent Application Ser. No. 412,042, filed Nov.

1973, now abandoned. Patent Application Ser. No.

1973. Patent Application Ser. No.

This invention relates to an improved arrangement fastening togetherintersecting members of a metal wall section, particularly such sectionsthat are in the form of modules that are prefabricated at aprefabn'cation station and are carried to a construction site where themodules are assembled to form a building, particularly a low-costresidence.

BACKGROUND OF THE INVENTION In the prefabrication of a sheet metal wallmodule of the character to which the present invention pertains, aseries of parallel studs with pairs of parallel longitudinal sideflanges are telescoped at their upper ends into an upper horizontal capmember having a pair of parallel longitudinal dependent side flanges andat their lower ends into a lower horizontal floor cap member having apair of parallel longitudinal upright side flanges. Thus, the sideflanges of each stud are in intimate surface contact with the sideflanges of the upper and lower horizontal members so that there are tworectangular areas of two layers of sheet metal at each juncture of astud with a horizontal member. The metal studs normally simulate wooden2X4 units, thus having webs about 3% inches wide and flanges about 1%inches wide. The studs are preferably of C-shape though they may be ofother non-planar configuration. The cap members and track members alsonormally simulate 2X4 wooden members, thus also having webs with widthsof about 3% inches and flanges having widths of about 1% inches. The capand track members, however, are normally of U-shape.

Difierent expedients have been employed heretofore to join thelongitudinal flanges of the studs to the longitudinal flanges of the twohorizontal members at each juncture to result in an acceptably rigidwall module. For example, various fastener elements have been employedincluding sheet metal screws and blind rivets. In each instance, such afastener element necessarily protrudes beyond the outer surface of acorresponding longitudinal flange of an upper or lower longitudinalmember and to that extent interferes with the fastening of sheetmaterial to finish a building wall. In addition, it

364,293, filed May 29,

364,294, filed May 29,

is necessary to provide a supply of fastener elements and to take timeto handle them.

There has been a pressing need for a sheet metal joint for use in aprefabricated metal sheet wall module that eliminates the need for usingsuch fastening elements. This need might be achieved by utilizing acrimping system such as that disclosed in British Pat. No. 145,380 orUS. Pat. No. 3,010,199, or US. Pat. No. 3,320,843. In fact, tools thathave heretofore been on the market, have been employed to produce crimpslike that shown in British Pat. No. 145,3 at the junctures of studs andhorizontal members of wall sections. Such operations, however, have beenperformed on site and as far as is known, have not been successfullyapplied to the prefabrication of wall section modules that are to betransported from a prefabrication station to the construction site.

SUMMARY OF THE INVENTION In this invention, a particular type of crimpjoint is formed by a crimping, or staking, operation at the junctures ofthe prefabricated wall sections while the components of theprefabricated wall sections are held together under compression. Thewall section modules so formed provide a module of sufficiently rigidconstruction to facilitate its being readily carried to a constructionsite and there assembled. Even though the crimp joint per se may not beas strong as a conventional fastener such as a screw or a rivet, therequired strength for the final wall is achieved by the installation ofgypsum board or other sheeting material in place to form the completedwall of the residence and the precompressed condition holds the studs infirm contact with the cap member and the track member, thus making itunnecessary for the crimp joint itself to be strong enough to supportany substantial part of the vertical load to which the studs aresubjected. While such precompression effects have existed heretoforewhen using screws or rivets, advantage is now taken of those effects topermit the use of crimp joints. By using a crimp joint of the typedescribed herein, a less expensive but satisfactory prefabricated moduleis made available without dangerous reduction of strength of the finalwall structure in which it is incorporated.

The invention employs a particular crimp joint to interconnect thelongitudinal flanges of the sheet metal studs and the longitudinalflanges of the upper and lower horizontal members of a prefabricatedwall module. This particular crimp joint has been employed for otherpurposes prior to the date of conception of the present invention butthe present invention resides in the discovery that all of the variouspotential advantages of that crimp joint may be fully utilized for thefirst time to hold vertical studs in place between a cap member and atrack member of a sheet metal wall module.

In the fabrication of such a crimp joint in the present invention, a diehaving a cavity is placed inside a stud against the inner surface of alongitudinal side flange of the stud and a punch is placed in registerwith the die against the outer surface of the longitudinal side flangeof an associated upper or lower longitudinal member of the wall module.Then the die and punch are squeezed together to cause the punch to forma pair of concurrent or aligned apertures in the two layers of sheetmetal with interlocking tongues extending from the periphery of theaperture in a direction about perpendicular to the two layers of sheetmetal and inwardly into the interior of the stud. Though crimps havingtongues of that configuration have been employed heretofore to fastentwo sheet metal parts together, they have not, so far as is known, beenemployed to fasten together two perpendicularly intersecting members ofa wall section module of the type described to hold them together undercompression.

The tongues employed in the present invention are of specialconfiguration, and unlike those employed heretofore in fastening twointersecting members of a wall structure together, extend generallytransversely or perpendicularly to the surface of the sheets fastenedtogether rather than generally parallel to or folded back onto thosesheets and are curved and have greater widths at their outer ends thanthey do at their roots where they are joined to the sheets that arecrimped together. The cross-sections of the tongues in a plane parallelto the surfaces of the sheet metal members fastened together, are ofoutwardly concave generally hyperbolic configuration and adjacenttongues formed from the two pieces of sheet metal are nested together incontacting interlocking fashion. The sharpness of curvature of thehyperbolic cross-sections gradually increases with the distance from thefastened surfaces thereby forming a tightly interlocked pair of tonguesthat are restrained from relative movement in any direction, eitherparallel to or transverse to the axis of the apertures. Furthermore, theouter ends, or comers of the tongues, remote from the members fastenedtogether, lie outside or beyond the edge or projection of the aperture.The tongue may be described as being of hyperboloidal configuration.

The special synergistic relation of such a crimp joint to the specificstructure of a sheet metal wall module of the character described, maybe appreciated by considering various advantages of the new combination.

The most important advantage lies in the fact that such crimp joints maybe employed to provide portable lower cost wall modules while stillmeeting standard building requirements for the ultimate strength of thewalls formed in housing in which they are assembled.

A further advantage, of course, lies in the elimination of need forstocking and handling separate fastener elements.

An important advantage lies in the fact that the time required to formthe crimp joints in a prefabricated wall section module is reduced,compared with the time required when the joints are formed with the aidof screws or rivets, thereby reducing the cost of manufacture of wallstructures, a very important consideration in low-cost housingconstruction.

A still further advantage of the invention resides in the fact that theprojecting heads of screws and rivets are eliminated, thus facilitatingflat engagement of wallboard or other material with the outer surfacesof the wall sections.

Another advantage resides in the fact that the tongues so formed liewithin the interior of the wall section in a location where the sharpedges of the tongues provide very little hazard to workmen who handlethe wall section module. Commonly, the studs of a sheet metal wallmodule are Cshaped in cross-sectional configuration with inwardly turnedstiffening lips formed at the edges of the side flanges of the studs. Asa result, in such a structure the stiffening lips of the studs make theextended tongues of the crimped joints even less accessible. Suchstiffening lips of the studs aid in reducing the hazards to workmen.

To produce the prestressed joints, care is taken that the opposite endedges of each stud are perpendicular to the longitudinal axis of thestud and are squarely seated in pressure contact with the main web ofthe upper and lower horizontal members respectively. The crimp joints atthe opposite ends of the stud are formed while the assembly is preloadedin this manner and the crimp joints have such inherent effectivenessagainst relative movement that the crimp joints effectively capture theprestressing forces and maintain the prestressing in the resultantmodules and in the finished wall of a building.

In a sheet wall module of the present construction, crimping isperformed at a point midway between the edges of the longitudinal sideflanges of the studs and less than about one inch from the web of thehorizontal Cshaped member, into which the stud is pressed. The formingof the crimp is performed by means of a pair of cooperating jaws of apower-actuated hand tool, the hollow die being carried by one jaw andthe cooperating punch being carried by the other jaw.

It is a simple matter to design such a pair of jaws with the desiredreach and, moreover, to shape the jaws to straddle and clear astiffening lip of a longitudinal side flange of a sheet metal stud.Employing such a tool makes it possible to fabricate a crimp joint inprestressed sheet metal in an operation of less than about one secondduration and thus minimizes the cost of shop assembly of a prefabricatedsheet metal wall module.

The present invention is based on the discovery that within thelimitation imposed by the width dimension of a side flange of a stud, itis possible to fabricate a crimp joint that is of adequate strength as ajoint per se without unduly lowering the strength of the stud itself. Ithas been found that if the diameter of the aperture is substantiallyless than three-eighths inch, the crimp joint itself is too weak and onthe other hand, if the cross-dimension substantially exceedsthree-eighths inch, the stud itself is unduly weakened. In the bestpractice of the invention wherein the inside diameter of the die cavityis approximately seven-sixteenths inch and wherein the area of theaperture produced by a punch exceeds the cross-sectional area of thepunch, it has been found that the aperture is too large if the diameterof the punch is substantially greater than about five-sixteeths inch andthe diameter of the aperture is too small if the diameter of the punchis substantially less than about three-sixteenths inch.

DRAWINGS The various features and advantages of the invention may beunderstood from the following detailed description and the accompanyingdrawings:

FIG. 1 is a perspective view of a part of a residential home duringconstruction showing part of the framing of the house that incorporatesthe present invention;

FIG. 2 is a perspective view of a pair of wall section modules in theframing shown in FIG. 1;

FIG. 3 is a perspective view showing a poweractuated hand tool and acrimp joint that is produced by the tool;

FIG. 4 is a sectional view showing how the poweractuated hand toolpenetrates two layers of sheet metal to join the two layers by a crimpjoint;

FIG. 5 is a view similar to FIG. 4 taken at from the position shown inFIG. 4;

FIG. 6 is a face view of the inner side of a crimp joint as seen alongthe line 66 of FIG. 4;

FIG. 7 is a sectional view of the crimp joint as seen along the line 77of FIG. 6;

FIG. 8 is a face view of the outer side of the crimp joint as seen alongthe line 8--8 of FIG. 7;

FIG. 9 is a fragmentary side elevational view showing a crimp joint atthe juncture of a stud and a flange of a track member into which thelower end of the stud telescopes;

FIG. 10 is a sectional view taken along the line 10l0 of FIG. 9;

FIG. 11 is a broken away sectional view illustrating the manner in whichthe structure of a prefabricated wall module is preloaded at the upperand lower ends of a stud while the crimp joints are being formed;

FIG. 12 is a sectional view taken along the line 12l2 of FIG. 11; and

FIG. 13 is an elevational view of another form of tool that has beenemployed to form crimped joints in this invention.

GENERAL DESCRIPTION Outline In the following description, the actualassembly of the prefabricated wall sections of this invention in a houseis first described. Then, typical wall section modules made inaccordance with the invention are described. And finally, the crimpingsystem is described in some detail.

House Assembly 7 FIG. 1 is a perspective view of a typical residentialhouse which has been partially framed with a framing systemincorporating this invention. The load-bearing wall section module 10and non-load-bearing wall section modules 14, 15, and 16 are shown insome detail. Wall section modules 10, 14, 15 and 16 that have beenprefabricated in accordance with this invention at a plant remote fromthe building construction site, are transportedto the buildingconstruction site by truck. Wall section modules 10, 14, 15 and 16 arethen carried by hand from the truck, stood up on the house floor F, andheld in standing position while they are secured to the floor F and toeach other. A superstructure, such as a roof, is mounted so that theload per unit length applied to the load-bearing modules is greater thanthe load per unit length supplied to the non-loadbearing modules.

Wall section modules 10, 14, 15, and 16 are typically 16 or feet inlength and 8 to 10 feet high. In the best embodiment of the invention,the wall section modules are 16 feet long, 8 feet high, and about 3%inches wide, and they are made of steel members that simulate 2X4 woodenmembers. Such a wall section module is easily handled by three men.

If the floor F of the house consists of a concrete slab, the wallsection modules may be secured to the floor slab in a well-known mannerby shooting pins through suitable washers and through the webs of thesheet metal floor track members of the wall section modules into theconcrete floor slab. If the floor F is wooden, the wall section modulesmay be secured to the floor F by nailing through the webs of the bottomcap members of the wall section modules. The wall section modules arethen suitably secured to adjacent wall section modules, and wallboard Wis secured to the wall section module by screws 19 or other suitablefasteners (see FIG. 2).

Wall Section Modules FIG. 2 shows wall section modules 16 in greaterdetail. Wall section module 16 is composed of a downwardly facingelongated channeled cap member 20, which provides the top of the wallsection module 16, and upwardly facing elongated channeled floor trackmember 22, which provides the bottom of the wall section module 16. Capmember 20 and floor track member 22 are positioned horizontally aboveand below metal studs 25 respectively and, in the illustrated embodimentof the invention, are both about 20 feet in length. The cap member 20,the floor track member 22, and the studs 25 may all be made of 26-gaugegalvanized steel both in the non-load-bearing walls and in theload-bearing walls.

The top cap member 20 and the lower track member 22 are typicallyU-shaped channeled metal members. Cap member 20 has an elongated mainweb 26 and downwardly depending longitudinal side flanges 28 integralwith the main web 26. Floor track 22 has an elongated main web 30 andupstanding flanges 32 extending longitudinally of and integral with themain web 30.

As shown in FIG. 2, a series of parallel channeled studs 25 are securedvertically between the cap member 20 and the floor track member 22 every16 or 24 inches. In this invention, they are secured together by specialcrimps at their intersections (see, for example, FIGS. 3 and 6-11). Inthe best mode of practicing this invention, studs 25 are C-shapedchanneled members as shown in FIGS. 3 and 12, each of which has a mainweb 34 and relatively narrow flanges 35 extending longitudinally of andintegral with the mainweb 34.

In the illustrated embodiment of the invention, -studs 25 are alsoprovided with inwardly projecting stiffening flange lips 36 and returns38, extending along the length of and integral with flanges 35 (.seeFIG. 12). It is common practice to attach wallboard W and thelike toflanges 35 of studs 25 by means of screws 19 passing through the flanges35 (see FIG. 2). stiffening lips 36 and returns 38 provide structuralstrength to studs 25 and also provide rigidity toflanges 35 so that theywill not bend inwardly towards each other when subjected to the force ofthe screws 19 when wallboard W is screwed to the studs 25. v

Top plates 40 and 41 in the form of 2X4 wooden members are secured tothe upper cap web 26 by nails or the like. The lower top plates 40typically extend continuously from one end of cap member 20 to theother. Upper top plate 41 usually terminates short of the ends of thewall section module. This allows the wall section modules to be securedtogether easily at the construction site by nailing additional 2 X 4wooden members to the lower top plates 40 between the ends of the uppertop plates 41 of two adjacent wall section modules.

Studs 25 have rows of apertures 42 spaced longitudinally along thelength of the main web 34. These apertures 42 are provided to allow forthe convenient passage of electrical conduits, structural members, andthe like (not shown) through thestuds 25.

Wall section module 16 has an aperture or window 50 formed in the wallsection module. The window 50 is defined by an uninterruptedweight-bearing stud 52 on each side of the window, by a lintel 54 acrossthe top 7 of the window, and by a sill 56 across the bottom of thewindow. An uninterrupted stud 52 is one which extends continuouslybetween the cap member and the floor track member 22.

The lintel 54 and sill 56 are U-shaped channeled sheet metal membershaving upwardly and downwardly extending side flanges respectively. Thelintel 54 and the sill 56 are secured to the flanges of the studs 52 oneither side of the window 50 by screws 57 or the like.

Upper cripples 58 and lower cripples 60 are shortened studs which havebeen fitted and secured by screws 57 between the cap 20 and the lintel54 and between the sill 56 and floor track member 22 respectively.

A header 62 is secured over the window 50. The webs of the uppercripples 58 are cut away at their upper ends in order to receive theheader 62. The header 62 consists of a pair of inwardly facing mutuallyconfronting U-shaped channeled members of 20-gauge steel or the like.The header 62 is typically about 8 inches in .height. The top of theheader 62 is welded flush with the top of the studs 52 so that theheader will support the web 26 of the cap member 20 when installed.

As shown in FIG. 2, wooden 2X4 surrounds 78 are secured to the inside ofthe uninterrupted studs 52 on each side of the window aperture 50, tothe bottom of the lintel 54, and to the top of the sill 56 by nails.Surrounds 78 provide for the ready installation of jambs and the likefor window 50.

It is also contemplated that the joints in the frame members immediatelyadjacent window openings and door will be made with sheet metal screwsin a well known manner. Thus, around the window opening 50 sheet metalscrews are employed for the joints that involve the studs 52 immediatelyadjacent the opposite sides of the window opening, lintel 54, sill 56,cripples 58, 60, and header 62.

The Crimping System At all other junctures involving uninterruptedstuds, however, special crimp joints that characterize, the presentinvention are employed. They are of the .general character of the crimpjoints designated by numeral 89 in FIGS. 3-12. Thus, crimp joints 89 areemployed for connecting the upper ends of the uninterrupted studs to theupper cap members 20 and the lower floor track members 22 in both theload-bearing wall section modules and the non-load-bearing wall sectionmodules. The present invention is directed primarily to wall section,modules that incorporate crimp joints 89.

In FIGS. 3-12, the crimp joint 89 interconnects two layers of metal, forexample, 26-gauge galvanized steel, which two layers may be termed anouter layer 90 and an inner layer 92. At the juncture of a stud witheither an upper horizontal cap member 20 or a lower horizontal trackmember 22, the two longitudinal side flanges of the stud are inface-to-face contacting relation with the two longitudinal side flangesof the horizontal member.

Thus, in FIGS. 9 and 10, a longitudinal side flange 35 of a stud 25 ispositioned against a longitudinal side flange 32 of the lower horizontaltrack member 22 so that on each side of the stud there are two layers ofsheet metal in contacting relationship over a rectangular area that isdefined by the upper and lower edges 95 and 96, the longitudinal flange32 of the track member 8 22 and the parallel opposite edges 97 and 98 ofthe longitudinal side flange 30 of the stud. Thus, at each juncture of astud 25 with the lower track member 22, there are two rectangular areasof two layers of sheet material on the opposite sides respectively ofthe studs,

the longitudinal flange 32.0f the track member being the outer layer ofsheet metal in FIGS. 4-10 and the longitudinal side flange 35 of thestud being the inner layer 92 of sheet metal. Each of the crimp joints89 is located in a central portion of such a rectangle as may be seen inFIG. 9. Similar crimp joints are formed at the juncture of each studwith the cap member 20.

. As indicated in FIGS. 9 and 10, in this particular embodiment of theinvention, the outer edge of each longitudinal side flange 35 of eachstud 25 is formed with a previously mentioned inwardly turned stiffeninglip 36, the edge of which is bent back on itself to form a previouslymentioned return 38 so that the edge of the stiffening lip is smooth androunded.

The various crimp joints 89 shown in FIGS. 4-12 may be easily and almostinstantaneously fabricated by means of a power-actuated hand tool of thecharacter of the hand tool 100 in FIG. 5. The hand tool 100 which may beactuated by compressed air supplied by a hose 102 has a fixed jaw 104and a cooperating hinged jaw 105. The fixed jaw 104 carries a hollowdie, or socket, 106 which, as shown in FIGS. 4 and 5, has a cylindricalwall 108, and the hinged jaw 105 carries a cooperating punch which, asshown in FIGS. 6 and 7, comprises a punch 110. The pair of jaws has whatmay be termed a reach dimension designated A in FIG. 3, which is thedistance that the pair of jaws may reach beyond an edge of sheet metalthat the jaws straddle. The pair of jaws also has what may be termed astraddle clearance dimension B indicated in FIG. 3, which makes itpossible for the pair of jaws to reach beyond an obstacle that isstraddled by the jaws. The diagonal broken line 114 in FIG. 9 indicatesthe longitudinal axis Z-Z of the handtool 100 at a position taken by thehand tool to reach a central portion of the rectangular layers ofcontacting sheets of metal to form a crimp joint 89 at one end of a stud25, the two jaws of the tool straddlinga stiffening lip 36 of the studto make the crimp joint.

A stop (not shown) on the interior of the tool 100 limits the movementof the pivoted jaw 14 toward the stationary jaw 12, thus preventing thetines of the punch from striking the inside end of the bore of thehollow die 106.

With the hollow die or socket 106 abutting the inner layer 92 of the twolayers of metal actuation of the hand tool 100 causes the punch element110 to push through the two layers of metal to the limit position shownin FIGS. 4 and 5. The leading end of the punch element 1 10 has adiametrical cutting edge 116 formed by two pairs of opposite inclinedsurfaces which converge to form the cutting edge. A pair of inclinedsurfaces 1 15 are located on each of two opposite sides of the punch.These surfaces intersect at a line that is inclined to the longitudinalaxis of the punch at an angle of about 45. The two intersecting linesthemselves, corresponding respectively to each pair of incliriedsurfaces, intersect on the axis of the punch, thereby forming twodiverging cutting edges in a diametricalplane of the punch with thepoints at the outer periphery of the surface of the punch. In practice,there is a very narrow curve surface at each line of the intersection.The shape of the cutting edge 116 is best shown in profile in FIG. 5.

In fabricating a crimp joint 89, the punch 110 forms two concurrentapertures 118 in the two layers of metal. These apertures have across-sectional area slightly greater than the cross-sectional area ofthe punch. When the leading edge 116 of the punch element initiallypenetrates the two layers of metal, the two points form two holesrespectively. As the punch element continues to advance, the two layersof sheet metal tear in opposite directions as indicated by the two pairsof arrows A in FIG. 6. The result is the formation of two diametricallyopposite pairs of tongues that are of arcuate cross-sectionalconfiguration and two pairs of diametrically opposite rim flanges 125and 126. Each pair of tongues are nested together, as shown in FIG. 6.Each pair of rim flanges are also nested together. The two oppositetongues 122 are formed by the inner sheet metal layer 92 and the othertwo tongues 124 are formed by the outer sheet metal layer 90. The twotongues 124 extend through the inner aperture 118 and are curvedsufficiently to effectively interlock with the other two tongues 122.The initial diametrical cuts in the two layers of sheet metal form theend edges of the two pairs of tongues and the tearing of the two layersof metal in opposite directions form the side edges of the two pairs oftongues. Thus, the area of each tongue is approximately half the area ofeach aperture 118. The tongues 124 that extend through the aperture 118are wedge-shaped and of hyperboloidal configuration. The importance ofthis configuration is that the two tongues 124 enlarge in width fromtheir roots and extend beyond the periphery of the aperture 118 and thusinterlock with each other and with the apertures in the manner ofwedges. This arrangement makes it practically impossible to withdraw thetongues 124 of the outer sheet 90 through the aperture of the innersheet 92.

As may be seen in FIGS. 6 and 7, the projection of the corners of thetongues onto the two sheets 90 and 92 line outside the apertures andthen nest snugly together, very effectively interlocking to resistrelative movement of the metal sheets along their planes or pullingapart perpendicular to their planes. The forming of pairs of coaxialcrimp joints on opposite sides of the studs while the studs areprecompressed as described, provide a rigid structure at low cost.

The aperture so formed are not of circular configuration except alongthe rim flanges. The roots of the tongues have greater radii ofcurvature than the cylindrical punch, being nearly straight because ofthe bending action at the roots of the tongues. This is due to thetearing action along the sides of the tongues and the bending action atthe roots of the tongues.

As will be noted by reference to FIGS. 6 and 7, the shape of the tonguesin a plane PP parallel to the planes of the contacting areas of sheetmetal, are somewhat hyperbolic. Furthermore, the tongues are nearlystraight in such a plane near the roots of the tongues and the curvatureof these sections gradually increases, that is, the radius of curvatureof these sections gradu ally decreases, as the distance of the plane PPfrom the surfaces of the contacting metal sheets increases. They arealso somewhat hyperbolic in a plane perpendicular to the planes of thecontacting areas of the sheet metal. Thus, the tongues are ofhyperboloidal configuration.

During the crimping operation, the two pairs of tongues are confined bythe cylindrical wall 108 of the hollow die 106 so that at the end of themetal-forming operation the two pairs of tongues are more nearlyperpendicular to than parallel with the planes of the two layers ofmetal. As will be noted in FIGS. 4 and 7, the root portions of the twopairs of tongues are bent with rather small radii of curvature.Nevertheless, the metal of the two pairs of tongues are not subjected toexcessive bending stress about their roots and this fact partly accountsfor the strength of the finished crimp joint. It has been found,moreover, that with the wall section modules made of galvanized sheetsteel, for example, 26-gauge sheet steel, the non-corrosive coatings ofthe two layers of metal readily stretch or contract to smoothly followthe bending of the two tongues and thus generally remain unbroken tocontinue to protect the surfaces of the sheet metal at the roots of thetongues.

In the best mode of practicing the invention, the edges at the oppositeends of the studs 25 are formed accurately perpendicular to the lengthof the stud to permit the upper end of the stud to make snug abutmentagainst the main web 26 of the cap member 20 and to permit the lower endof the stud to make snug abutment with the main web 30 of the trackmember 22. In the practice of the invention, a pair of pressure membersindicated diagrammatically in FIG. 13 cooperate to place a stud undersubstantial longitudinal compression between the upper cap member 20 andthe lower cap member 22 at the time that the four crimp joints 89 two atthe top and two at the bottom, as illustrated in FIG. 11 are fabricatedto anchor the studs in assembled position. The two pressure members 130cooperate to place the stud 25 under longitudinal compression ofsubstantial magnitude to press the opposite ends of the stud intopressure contact with the main webs 26 and 30 of the cap member 20 andthe track member 22 respectively. When the sheet metal wall structure isreleased from the two pressure members 130 after the four crimp jointsare fabricated, the major intermediate longitudinal portion of the studrecovers from compression but the two pairs of crimp joints preventrecovery of the two opposite end portions of the stud from compression.Consequently, the two opposite ends of the stud remain preloaded, withresidual local longitudinal compression of each end of the studs opposedby corresponding coextensive local tension in the associate side flangesof the upper and lower horizontal members 20, 22.

The preloading of a sheet metal wall section module in this manner lendspreliminary stiffness to the wall module that is more than adequate tomaintain the desired assembled configuration of the wall module in r thecourse of transporting and otherwise handling the prefabricated wallmodule and during maneuvering of the wall module into assembled positionto form a portion of a wall at the building site. The subsequentaddition of skins in the form of wallboard or the like to opposite facesof the prefabricated wall module provides the final degree of stiffnessthat is required in the finished wall structure. The fact that the studsare held snugly by preloading against the horizontal cap member andtrack member makes it unnecessary for the crimp tongues themselves tosupport any of the load. For this reason, the crimps need only besufficiently strong to permit the prefabricated modules to be carriedfrom a prefabrication station to the construction site where the modulesare assembled to form walls of a house or similar structure.

The invention may be practiced with studs of other non-planarconfiguration. For example, they may be U-shaped instead of C-shaped incross section, that is, the stiffening flanges 36 may be omitted. Thestuds 25 may also be Z-shaped in cross section with parallel oppositeside flanges.

FIG. 13 shows an alternative tool which has been employed for makingcrimped junctures in accordance with this invention. This tool employs aso-called pressure cylinder 222 which has a piston (not shown) within itconnected to a shaft 224 having a punch at the outer end thereof andmovable coaxially with the cylinder by manipulation of air underpressure through the two passages that communicate with cavities withinthe cylinder on opposite sides of the piston. A yoke 240 on one end ofthe cylinder has an am 242 which supports a hollow die 244 coaxiallywith the cylinder and consequently coaxially with the punch. Inoperation between the hollow die and punch are located on opposite sidesof a pair of sheet metal members arranged as in FIGS. 3 and 9, themanipulation of air pressure in the cylinder causes the punch to piercethe overlapping areas of sheet metal and to enter the die to form acrimped joint as described hereinabove. While this type of tool can beemployed to form crimp joints of the type described, it is cumbersomeand awkward to use and hence not as suitable as the pneumatic rivetertype structure previously described in connection with FIG. 3.

The invention may be practiced in many ways other than thosespecifically described, all within the scope of the appended claims.

The invention claimed is:

l. A method of constructing a prefabricated wall module for a building,wherein the wall module comprises:

a first normally horizontal sheet metal member in the form of an upperU-shaped downwardly facing cap member having a main web and twolongitudinal side flanges depending from the main web;

a second normally horizontal sheet metal member in the form of a lowerU-shaped floor track member having a main web and two longitudinal sideflanges extending upward therefrom;

a plurality of horizontally spaced normally upright sheet metal studs,each having a main longitudinal web and two opposite side flangesextending from the main web,

the upper and lower ends of the studs being telescoped into the firstand second horizontal members respectively into pressure contact withthe main webs thereof with the two side flanges of each longitudinalmember in face-to-face relation with the side flanges of the studsthereby providing a pair of opposite rectangular areas of two layers ofsheet metal at each end of each stud,

the intersection of the side flanges of the studs with the side flangesof the two horizontal members forming 90 angles with the vertex of eachangle at a comer of one of said rectangular areas;

said method being characterized by the use of a power-actuated hand toolhaving two parts with the reach of the jaws at least equal to thedistance from said vertex to a central portion of the correspondingrectangular area,

one of the parts of the tool carrying a hollow die, the

other of the two parts carrying a punch to cooperate with the die;

said method including the steps of:

placing each stud in the desired assembled position relative to saidhorizontal members thereby providing two of said rectangular areas ateach end of the stud with one of said vertices at the corner of therectangular area;

applying pressure to said track member and said cap member to force thewebs of said members into pressure contact with the ends of said studs;

placing said tool in the region of each of said vertices with the partsextending diagonally of the corresponding rectangular area into acentral portion of the rectangular area and with said hollow die insidethe stud and said cooperating punch outside the stud;

and actuating the tool to drive said punch through the two layers ofmetal of the rectangular area into the interior of the die,

while the ends of said studs are held in pressure contact with the websof said longitudinal members,

said punch and die being shaped and dimensioned to form an aperture inthe two layers with interlocking tongues of the two layers projectingfrom the periphery of the aperture into the interior of the stud andwith the tongues more nearly perpendicular than parallel to the innersurface of the stud.

2. A method as set forth in claim 1 in which said punch is tapered fromopposite sides to form a diametrical leading edge with two inclinedleading surfaces on opposite sides of the leading edge to cause thepunch to form two diametrically opposite pairs of interlocking tonguesin the two layers of sheet metal with the tongues of the outer layer ofsheet metal interlocking with the tongues of the inner layer.

3. A method of constructing a prefabricated wall module for a building,wherein the wall module comprises:

a first normally horizontal sheet metal member in the form of an upperU-shaped downwardly facing cap member having a main web and twolongitudinal side flanges depending from the main web;

a second normally horizontal sheet metal member in the form of a lowerU-shaped floor track member having a main web and two longitudinal sideflanges extending upward therefrom;

a plurality of horizontally spaced normally upright sheet metal studs,each having a main longitudinal web and two opposite side flangesextending from the main web,

the upper and lower ends of the studs being telescoped into the firstand second horizontal members respectively into pressure contact withthe main webs thereof with the two side flanges of each longitudinalmember in face-to-face relation with the side flanges of the studsthereby providing a pair of opposite rectangular areas of two layers ofoverlapping sheet metal at each end of each stud,

the intersection of the side flanges of the studs with the side flangesof the two horizontal members forming angles with the vertex of eachangle at a corner of one of said rectangular areas;

said method being characterized by the use of a tool having two partswith the reach of the jaws thereof at least equal to the distance fromsaid vertex to a central portion of the corresponding rectangular area,

13 the two parts of the tool respectively carrying two cooperatingpunching elements, one being a hollow die, and the other being a punch;said method including the steps of:

placing each stud in the desired assembled position relative to saidhorizontal members thereby providing two of said rectangular areas ateach end of the stud with one of said vertices at the corner of therectangular area; applying pressure to said track member and said capmember to force the webs of said members into pressure contact with theends of said studs; placing said tool in the region of each of saidvertices with the parts extending diagonally of the correspondingrectangular area into a central portion of the rectangular area and withsaid two punching elements on opposite sides of the overlapping portionsof said sheet metal in said area;

and forcing said jaws together to drive said punch through the twolayers of metal of the rectangular area into the interior of the die,

while the ends of said studs are held in pressure contact with the websof said longitudinal members,

said punch and die being shaped and dimensioned to form an aperture inthe two layers with interlocking tongues of the two layers projectingfrom the periphery of the aperture into the interior of the stud andwith the tongues more nearly perpendicular to than parallel to the innersurface of the stud.

4. A method as set forth in claim 3 in which said punch is tapered fromopposite sides to form a diametrical leading edge with two inclinedleading surfaces on opposite sides of the leading edge to cause thepunch to form two diametrically opposite pairs of interlocking tonguesin the two layers of sheet metal with the tongues of the outer layer ofsheet metal interlocking with the tongues of the inner layer.

1. A method of constructing a prefabricated wall module for a building,wherein the wall module comprises: a first normally horizontal sheetmetal member in the form of an upper U-shaped downwardly facing capmember having a main web and two longitudinal side flanges dependingfrom the main web; a second normally horizontal sheet metal member inthe form of a lower U-shaped floor track member having a main web andtwo longitudinal side flanges extending upward therefrom; a plurality ofhorizontally spaced normally upright sheet metal studs, each having amain longitudinal web and two opposite side flanges extending from themain web, the upper and lower ends of the studs being telescoped intothe first and second horizontal members respectively into pressurecontact with the main webs thereof with the two side flanges of eachlongitudinal member in face-to-face relation with the side flanges ofthe studs thereby providing a pair of opposite rectangular areas of twolayers of sheet metal at each end of each stud, the intersection of theside flanges of the studs with the side flanges of the two horizontalmembers forming 90* angles with the vertex of each angle at a corner ofone of said rectangular areas; said method being characterized by theuse of a power-actuated hand tool having two parts with the reach of thejaws at least equal to the distance from said vertex to a centralportion of the corresponding rectangular area, one of the parts of thetool carrying a hollow die, the other of the two parts carrying a punchto cooperate with the die; said method including the steps of: placingeach stud in the desired assembled position relative to said horizontalmembers thereby providing two of said rectangular areas at each end ofthe stud with one of said vertices at the corner of the rectangulararea; applying pressure to said track member and said cap member toforce the webs of said members into pressure contact with the ends ofsaid studs; placiNg said tool in the region of each of said verticeswith the parts extending diagonally of the corresponding rectangulararea into a central portion of the rectangular area and with said hollowdie inside the stud and said cooperating punch outside the stud; andactuating the tool to drive said punch through the two layers of metalof the rectangular area into the interior of the die, while the ends ofsaid studs are held in pressure contact with the webs of saidlongitudinal members, said punch and die being shaped and dimensioned toform an aperture in the two layers with interlocking tongues of the twolayers projecting from the periphery of the aperture into the interiorof the stud and with the tongues more nearly perpendicular than parallelto the inner surface of the stud.
 2. A method as set forth in claim 1 inwhich said punch is tapered from opposite sides to form a diametricalleading edge with two inclined leading surfaces on opposite sides of theleading edge to cause the punch to form two diametrically opposite pairsof interlocking tongues in the two layers of sheet metal with thetongues of the outer layer of sheet metal interlocking with the tonguesof the inner layer.
 3. A method of constructing a prefabricated wallmodule for a building, wherein the wall module comprises: a firstnormally horizontal sheet metal member in the form of an upper U-shapeddownwardly facing cap member having a main web and two longitudinal sideflanges depending from the main web; a second normally horizontal sheetmetal member in the form of a lower U-shaped floor track member having amain web and two longitudinal side flanges extending upward therefrom; aplurality of horizontally spaced normally upright sheet metal studs,each having a main longitudinal web and two opposite side flangesextending from the main web, the upper and lower ends of the studs beingtelescoped into the first and second horizontal members respectivelyinto pressure contact with the main webs thereof with the two sideflanges of each longitudinal member in face-to-face relation with theside flanges of the studs thereby providing a pair of oppositerectangular areas of two layers of overlapping sheet metal at each endof each stud, the intersection of the side flanges of the studs with theside flanges of the two horizontal members forming 90* angles with thevertex of each angle at a corner of one of said rectangular areas; saidmethod being characterized by the use of a tool having two parts withthe reach of the jaws thereof at least equal to the distance from saidvertex to a central portion of the corresponding rectangular area, thetwo parts of the tool respectively carrying two cooperating punchingelements, one being a hollow die, and the other being a punch; saidmethod including the steps of: placing each stud in the desiredassembled position relative to said horizontal members thereby providingtwo of said rectangular areas at each end of the stud with one of saidvertices at the corner of the rectangular area; applying pressure tosaid track member and said cap member to force the webs of said membersinto pressure contact with the ends of said studs; placing said tool inthe region of each of said vertices with the parts extending diagonallyof the corresponding rectangular area into a central portion of therectangular area and with said two punching elements on opposite sidesof the overlapping portions of said sheet metal in said area; andforcing said jaws together to drive said punch through the two layers ofmetal of the rectangular area into the interior of the die, while theends of said studs are held in pressure contact with the webs of saidlongitudinal members, said punch and die being shaped and dimensioned toform an aperture in the two layers with interlocking tongues of the twolayers projecting from the periphery of the aperture into the interiorof the stud anD with the tongues more nearly perpendicular to thanparallel to the inner surface of the stud.
 4. A method as set forth inclaim 3 in which said punch is tapered from opposite sides to form adiametrical leading edge with two inclined leading surfaces on oppositesides of the leading edge to cause the punch to form two diametricallyopposite pairs of interlocking tongues in the two layers of sheet metalwith the tongues of the outer layer of sheet metal interlocking with thetongues of the inner layer.